Re: [Lsr] New draft on Flex-Algorithm Bandwidth Constraints

[William Britto A J <[e-mail]>]

Hi Robert,

Thanks for your comments.

Currently there are customers who deploy separate networks, of which one could be assigned metrics relative to the interface bandwidths, while other could be based on other parameters like latency, etc. Flex-Algo which facilitates different metric-types for SPF, is a very useful feature for such network consolidation use-cases. We are trying introduce the protocol constructs to simplify the use of metric based on bandwidth via Flex-Algo.

Any existing tools and techniques used by operators who configure metric relative to link bandwidth to optimize the network can be used with these Flex-Algo constructs too. The Flex-Algo bandwidth constraints defined here can be used to automatically derive a metric based on reference bw vs link bw; and if required, this can be overridden using the individual link bandwidth-metric sub-TLV. We will make this clear in the next version.

RFC 8570 support advertising link delay parameters in ISIS. Protocols like TWAMP support dynamically measuring the delay. Whether egress queueing delay is included in the link delay depends on the measuring mechanism. The Exclude Max Delay sub-TLV introduced in this draft is only meant for pruning out high latency links from a Flex-Algo, and it is upto the operator to define the maximum bounds based on the measuring mechanisms deployed in his network.

Thanks,
William

From: Robert Raszuk <[e-mail]>
Date: Saturday, 27 February 2021 at 5:54 PM
To: William Britto A J <[e-mail]>
Cc: [e-mail] <[e-mail]>, Rajesh M <[e-mail]>, Shraddha Hegde <[e-mail]>, DECRAENE Bruno IMT/OLN <[e-mail]>
Subject: Re: [Lsr] New draft on Flex-Algorithm Bandwidth Constraints
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Hi William & co-authors,

I read the draft and have two basic questions.

1.
Both bw & delay can be used as defined in the draft to construct new forwarding topologies. But how practical such topologies would be in the real life when 40GB links may be heavily occupied with bursty traffic and 10G links can sit idle ? I suppose you are trying to address the case where say 12 gbps holographic stream needs to be sent across a network.. But then I don't think if sending it in a single flow instead of spreading into many sub-flows and use as much as possible ecmp would not be a better option.

2.
Likewise how good is my accumulated link delay value if in between there are deep buffer network elements and say egress queuing to each link (which max is unaccounted for in your draft) can significantly alter the end to end delay ? Have you consider to add MAX_EGRESS_QUEUE_DELAY on a per link basis (still as static value).  So if some traffic is delay sensitive we will have a much better accuracy not to get into a trap of queuing related delays.

Thx a lot,
Robert.


On Fri, Feb 26, 2021 at 8:37 AM William Britto A J <bwilliam=[e-mail]<mailto:[e-mail]>> wrote:
All,

We would like to draw your attention to a new ID: https://datatracker.ietf.org/doc/html/draft-hegde-lsr-flex-algo-bw-con-00<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-hegde-lsr-flex-algo-bw-con-00__;!!NEt6yMaO-gk!WgwtY1NpSXZkAtkBfmMRfgZABaIBWv534VYF7vvI4eGGuMbmdKMK_VpWFKV2Tba5Qg$>

The draft talks about introducing link bandwidth related constraints in Flex-Algorithm which can be used to define a Flex-Algorithm based on bandwidth based metric.

Please review. Any questions and comments are welcome.

Thanks,
William


From: [e-mail]<mailto:[e-mail]> <[e-mail]<mailto:[e-mail]>>
Date: Monday, 22 February 2021 at 10:56 PM
To: Bruno Decraene <[e-mail]<mailto:[e-mail]>>, Rajesh M <[e-mail]<mailto:[e-mail]>>, Rajesh M <[e-mail]<mailto:[e-mail]>>, Shraddha Hegde <[e-mail]<mailto:[e-mail]>>, William Britto A J <[e-mail]<mailto:[e-mail]>>, William Britto A J <[e-mail]<mailto:[e-mail]>>
Subject: New Version Notification for draft-hegde-lsr-flex-algo-bw-con-00.txt
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A new version of I-D, draft-hegde-lsr-flex-algo-bw-con-00.txt
has been successfully submitted by Shraddha Hegde and posted to the
IETF repository.

Name:           draft-hegde-lsr-flex-algo-bw-con
Revision:       00
Title:          Flexible Algorithms Bandwidth Constraints
Document date:  2021-02-22
Group:          Individual Submission
Pages:          21
URL:            https://urldefense.com/v3/__https://www.ietf.org/archive/id/draft-hegde-lsr-flex-algo-bw-con-00.txt__;!!NEt6yMaO-gk!QGg36p91zPfVMznYY91xs-zx70Qp5BE1nJx-Thnl14sTCkvwgOjEzjGBtD3v6TruoA$<https://urldefense.com/v3/__https:/www.ietf.org/archive/id/draft-hegde-lsr-flex-algo-bw-con-00.txt__;!!NEt6yMaO-gk!QGg36p91zPfVMznYY91xs-zx70Qp5BE1nJx-Thnl14sTCkvwgOjEzjGBtD3v6TruoA$>
Status:         https://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft-hegde-lsr-flex-algo-bw-con/__;!!NEt6yMaO-gk!QGg36p91zPfVMznYY91xs-zx70Qp5BE1nJx-Thnl14sTCkvwgOjEzjGBtD1VexjHPQ$<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-hegde-lsr-flex-algo-bw-con/__;!!NEt6yMaO-gk!QGg36p91zPfVMznYY91xs-zx70Qp5BE1nJx-Thnl14sTCkvwgOjEzjGBtD1VexjHPQ$>
Htmlized:       https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/draft-hegde-lsr-flex-algo-bw-con__;!!NEt6yMaO-gk!QGg36p91zPfVMznYY91xs-zx70Qp5BE1nJx-Thnl14sTCkvwgOjEzjGBtD3X5nPQbA$<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/html/draft-hegde-lsr-flex-algo-bw-con__;!!NEt6yMaO-gk!QGg36p91zPfVMznYY91xs-zx70Qp5BE1nJx-Thnl14sTCkvwgOjEzjGBtD3X5nPQbA$>
Htmlized:       https://urldefense.com/v3/__https://tools.ietf.org/html/draft-hegde-lsr-flex-algo-bw-con-00__;!!NEt6yMaO-gk!QGg36p91zPfVMznYY91xs-zx70Qp5BE1nJx-Thnl14sTCkvwgOjEzjGBtD2aqSYcuQ$<https://urldefense.com/v3/__https:/tools.ietf.org/html/draft-hegde-lsr-flex-algo-bw-con-00__;!!NEt6yMaO-gk!QGg36p91zPfVMznYY91xs-zx70Qp5BE1nJx-Thnl14sTCkvwgOjEzjGBtD2aqSYcuQ$>


Abstract:
   Many networks configure the link metric relative to the link
   capacity.  High bandwidth traffic gets routed as per the link
   capacity.  Flexible algorithms provides mechanisms to create
   constraint based paths in IGP.  This draft documents a set of
   bandwidth related constraints to be used in Flexible Algorithms.





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